1. Field of the Invention
The present invention relates to a folding and shape-forming apparatus for a prepreg, and more particularly to a folding and shape-forming apparatus for a prepreg which can shape the prepreg using vacuum pressure.
2. Description of the Related Art
Generally, the prepreg is a term for pre-impregnated composite fibers made by impregnating a highly elastic reinforced member, such as glass fiber, carbon fiber, Kevlar fiber, or the like with a base member, such as unsaturated polyester, epoxy resin, polyamide resin, or the like in a uniform rate. The prepreg is used in various industries which require high strength and elasticity, such as various kinds of sports machines, air planes, boats, or the like.
The prepreg must undergo a shape-forming process to have a form appropriate for the use thereof.
FIG. 1 is a schematic view illustrating a folding and shape-forming apparatus for a prepreg according to the conventional art. FIG. 2 is an operation status view illustrating operation status of the conventional folding and shape-forming apparatus for a prepreg.
As shown in FIG. 1, the folding and shape-forming apparatus for a prepreg according to the conventional art includes a vacuum chamber 10 which can create a vacuum state, an expanding portion 20 disposed inside the vacuum chamber 10, provided with a stack of prepregs P thereon, and expanding by inside vacuum pressure of the vacuum chamber 10, a heating portion 30 disposed inside the vacuum chamber 10 and heating the prepregs P for shape-formation of the prepregs, and a mandrel 40 which presses one upper side of the stack of prepregs P.
The upper surface of the vacuum chamber 10 is provided with a cover 11 so that the prepregs P can be put into and taken out of the vacuum chamber 10 through the cover 11.
The expanding portion 20 is placed under the vacuum chamber 10 in a flat form.
Operation of the conventional folding and shape-forming apparatus for a prepreg will be described below.
First, the stack of prepregs P to be shape-formed is disposed on the upper surface of the expanding portion 20 after opening the cover 11, and then the mandrel 40 is placed on one side of the upper surface of the stack of prepregs P.
After that, the cover 11 is closed and the vacuum chamber 10 is sealed. Next, an inside temperature of the vacuum chamber 10 is raised by starting the heating portion 30 so that the inter-layer slipping of the stack of prepregs P does not occur.
Next, vacuum pressure is applied to the vacuum chamber 10 so that the expanding portion 20 expands.
As shown in FIG. 2, when the expanding portion 20 is in an expanded state, some portion of the prepregs P other than a portion of the prepregs P on which the mandrel 40 is placed is folded by expansion of the expanding portion 20.
That is, the prepregs P are folded at edges thereof disposed under the mandrel 40. If the vacuum status inside the vacuum chamber 10 develops further and the inside vacuum status of the vacuum chamber 10 reaches a high degree, the folded portion of the prepregs P contacts the side of the mandrel 40.
As described above, the strength of the vacuum of the vacuum chamber 10 is gradually reduced after the folding of the prepregs P is completed, and the expanding portion 20 is recovered to the flat form as the vacuum pressure is eliminated.
Since the conventional folding and shape-forming apparatus for a prepreg has a structure which can shape the stack of prepregs 20 only because of the expanding force of the expanding portion 20, it is difficult to form the shape of prepregs P when the stack of the prepregs P is of a large thickness, for example, when the stack of prepregs P includes 20 or more layers of prepregs P.
Further, since the conventional folding and shape-forming apparatus for a prepreg P cannot transfer sufficient pressure to a corner of the mandrel 40 when folding the stack of prepregs being of a large thickness, there is a problem in that a folding portion of the prepreg product is likely to be wrinkled.
The conventional folding and shape-forming apparatus for a prepreg can shape the prepreg only in a straight form. That is, it has a drawback of it being difficult to shape the prepreg into a curved form or to produce a prepreg product having a plurality of folds or having a curved contour.
Furthermore, in the conventional folding and shape-forming apparatus for a prepreg P, since the prepreg P before shape-formation and the prepreg P after the shape-formation are put in and taken out via the cover 11, it is impossible to set up an automatic manufacturing process, so that productivity of the prepreg product is not good.